The Effects of Perceptual Load on a Simon Task

Perceptual load (PL) hypothesis claims that PL is the determining factors of attentional selection. When PL is high, attentional resources are exhausted to process stimuli, resulting in no compatibility effect. When PL is low, attentional resources spill over to process a response-related distractor, resulting in a compatibility effect. A question is whether or not the PL effect can be generalized to other types of interference tasks, such as the Simon task. The Simon effect refers to the finding that reaction times are typically shorter when the stimulus location and response location are compatible than when they are incompatible, even if the stimulus location is irrelevant. Therefore, if PL has effects in the Simon task, then we expect a compatibility effect for low PL condition but not for the high PL condition. Participants performed the Simon task with three levels for the factor of PL (No PL, Low PL, and High PL). In the No PL condition, a target letter is presented alone; therefore, this is a typical Simon task. In the Low PL condition, three Os were presented as distractors. In the High PL condition, three distractors were heterogeneous. There were significant compatibility effects for the No PL and Low PL conditions; however, there was no compatibility effect for the High PL condition. The results supported our prediction that PL has a role in attentional selection in the Simon task. The results are also consistent with the attention-shift account of the Simon effect